42 U.S. Code § 12148 - Public transportation programs and activities in existing facilities and one car per train rule
With respect to existing facilities used in the provision of designated public transportation services, it shall be considered discrimination, for purposes of section 12132 of this title and section 794 of title 29, for a public entity to fail to operate a designated public transportation program or activity conducted in such facilities so that, when viewed in the entirety, the program or activity is readily accessible to and usable by individuals with disabilities.
Paragraph (1) shall not require a public entity to make structural changes to existing facilities in order to make such facilities accessible to individuals who use wheelchairs, unless and to the extent required by section 12147(a) of this title (relating to alterations) or section 12147(b) of this title (relating to key stations).
Paragraph (1) shall not require a public entity to which paragraph (2) applies, to provide to individuals who use wheelchairs services made available to the general public at such facilities when such individuals could not utilize or benefit from such services provided at such facilities.
Subject to paragraph (2), with respect to 2 or more vehicles operated as a train by a light or rapid rail system, for purposes of section 12132 of this title and section 794 of title 29, it shall be considered discrimination for a public entity to fail to have at least 1 vehicle per train that is accessible to individuals with disabilities, including individuals who use wheelchairs, as soon as practicable but in no event later than the last day of the 5-year period beginning on the effective date of this section.
In order to comply with paragraph (1) with respect to the remanufacture of a vehicle of historic character which is to be used on a segment of a light or rapid rail system which is included on the National Register of Historic Places, if making such vehicle readily accessible to and usable by individuals with disabilities would significantly alter the historic character of such vehicle, the public entity which operates such system only has to make (or to purchase or lease a remanufactured vehicle with) those modifications which are necessary to meet the requirements of section 12142(c)(1) of this title and which do not significantly alter the historic character of such vehicle.
The effective date of this section, referred to in subsec. (b)(1), probably means the effective date of subsec. (b), which is effective on date of enactment of Pub. L. 101–336, which was approved July 26, 1990. The effective date of subsec. (a) is 18 months after July 26, 1990. See section 231 of Pub. L. 101–336, set out as an Effective Date note under section 12141 of this title.